The present invention relates to an electrical apparatus comprising a box and an electro-acoustic transducer disposed in said box and exhibiting an active emission surface, said box comprising a bearing zone supporting an ear of a user, said bearing zone comprising an exit aperture of said electro-acoustic transducer, formed facing said active emission surface of said electro-acoustic transducer, said box furthermore comprising a decompression aperture made through said bearing zone.
Such an electrical apparatus is for example a mobile telephone. The electro-acoustic transducer is intended to reproduce the sound or speech messages received by the telephone.
In known mobile telephones, the electro-acoustic transducer is disposed directly inside the box of the telephone. The exit aperture of the electro-acoustic transducer is made in an outside wall of the box. This aperture allows the transmission of the acoustic wave from the transducer to the ear of the user. The wall through which the exit aperture of the electro-acoustic transducer is made forms the bearing zone for supporting the ear of the user.
Moreover, in this same bearing zone is made a decompression aperture enabling the pinna of the ear of the user to be placed in communication with the inside of the box or the ambient air. This decompression aperture ensures a balancing of the pressures between the ear of the user and the inside of the box or the ambient air. The decompression aperture caters only for a flow rate-pressure conversion in respect of the air stream produced by the transducer,
Pressure balancing is made possible by the intrinsic leaks present through the box. These leaks are formed at the level of the joints between the elements assembled to constitute the box, as well as through the passages defined in the box for the buttons of the keypad of the mobile telephone.
Such an electrical apparatus normally exhibits fairly mediocre acoustic qualities. In particular, it is very sensitive to variations in the contact leaks arising at the interface between the ear and the bearing zone supporting the ear on the box. These variations in the contact leaks in this region lead to variations in the frequency response which are highly prejudicial to listening quality.
In order to afford the user good acoustic quality, it is often necessary to implement an analogue or digital filtering of the signals received and addressed to the electro-acoustic transducer.
An aim of the invention is to propose an electrical apparatus comprising an electro-acoustic transducer disposed in the box, making if possible to obtain a frequency response of good quality and a weak sensitivity to variations in contact leaks formed between the ear and the box, without it being necessary to implement analogue or digital processing of the signal addressed to the transducer.
Accordingly, the subject of the invention is an electrical apparatus, of the aforesaid type, characterized in that said electrical apparatus comprises an essentially sealed resonant enclosure, inside which is disposed said electro-acoustic transducer, said enclosure delimiting a rear volume for said electro-acoustic transducer, in that said enclosure comprises an interference aperture made through a wall of said enclosure and a leakage aperture linking said rear volume to the outside of said enclosure, said interference aperture emerging outside said enclosure through said bearing zone, said leakage aperture emerging through a zone separate from said bearing zone, and in that said decompression aperture emerges outside said enclosure.
According to particular embodiments, the electrical apparatus comprising one or more of the following characteristics:
said wall of said enclosure constitutes at least a part of said bearing zone of said box;
said exit aperture of said electro-acoustic transducer is made through a wall delimiting both said enclosure and said box in a region of said bearing zone;
said exit aperture of said electro-acoustic transducer is made through a wall specific to said enclosure, said wall lying inside said box, and said exit aperture of said electro-acoustic transducer emerges inside an intermediate chamber of said box, said intermediate chamber being delimited at the rear of said decompression aperture made in said box;
said exit aperture of said electro-acoustic transducer and said decompression aperture are substantially aligned;
it comprises at least one tubular span extending at least one of said interference aperture, of said leakage aperture, of said exit aperture of said electro-acoustic transducer and of said decompression aperture;
at least one of said interference aperture, of said leakage aperture, of said exit aperture of said electro-acoustic transducer and of said decompression aperture comprises at least two disjoint orifices;
said electro-acoustic transducer is a loudspeaker;
the effective surface area of said interference aperture is substantially comprised between 0.1 mm2 and 1.6 mm2.
the effective surface area of said leakage aperture is greater than the effective surface area of said interference aperture;
the ratio of said effective surface area of said leakage aperture to said effective surface area of said interference aperture is substantially comprised between 1 and 8;
the ratio of the effective surface area of said decompression aperture to the effective surface area of said interference aperture is substantially greater than 16; and
it belongs to the group comprising:
a telephone; and
a portable electronic diary.